Pennelliiside D, a New Acyl Glucose from Solanum pennellii and Chemical Synthesis of Pennelliisides.

Acyl glucoses are a group of specialized metabolites produced by Solanaceae. Solanum pennellii, a wild-type tomato plant, produces acyl glucoses in its hair-like epidermal structures known as trichomes. These compounds have been found to be herbicides, microbial growth inhibitors, or allelopathic compounds. However, there are a few reports regarding isolation and investigation of biological activities of acyl glucoses in its pure form due to the difficulty of isolation. Here, we report a new acyl glucose, pennelliiside D, isolated and identified from S. pennellii. Its structure was determined by 1D NMR and 2D NMR, together with FD-MS analysis. To clarify the absolute configuration of the acyl moiety of 2-methylbutyryl in the natural compound, two possible isomers were synthesized starting from ß-D-glucose pentaacetate. By comparing the spectroscopic data of natural and synthesized compounds of isomers, the structure of pennelliiside D was confirmed to be 3,4-O-diisobutyryl-2-O-((S)-2-methylbutyryl)-D-glucose. Pennelliiside D and its constituent fatty acid moiety, (S)-2-methylbutanoic acid, did not show root growth-inhibitory activity. Additionally, in this study, chemical synthesis pathways toward pennelliisides A and B were adapted to give 1,6-O-dibenzylpennelliisides A and B.

Pennelliisides A-C, 2,3,4-Trisubstituted Acyl Glucoses Isolated from Solanum pennellii.

Solanum species accumulate a variety of secondary metabolites in their trichomes, and it is well known that acyl sugars are specialized metabolites secreted by the trichomes. However, very few reports provide detailed information on the chemical structure of polyacylated glucose derivatives, due to the α and ß isomerization that can occur at the C-1 position. In this study, a strategy was established to isolate polyacylated glucose derivatives. According to the developed strategy, hydroxy groups were derivatized to a benzyloxy group using TriBOT. After isolation of the compounds in pure form and deprotection of the benzyloxy group, the chemical structures of pennelliisides A-C were determined as 2,3,4-O-triisobutyryl-d-glucose, 3-O-(8-methylnonanoyl)-2,4-O-diisobutyryl-d-glucose, and 3-O-decanoyl-2,4-O-diisobutyryl-d-glucose, respectively. Structural elucidation was performed using spectroscopic techniques, including 1D and 2D NMR, FD-MS, and GC-MS. It was also found that the fatty acid moiety contributes to the allelopathic properties of the isolated compounds.